1. Field of the Invention
The present invention relates to an optical image-capturing lens assembly, and more particularly, to a compact optical image-capturing lens assembly used in an electronic product.
2. Description of the Prior Art
In recent years, with the popularity of portable electronic products featuring photographing function, the demand for compact imaging lenses is increasing, and the sensor of a general photographing camera is none other than CCD (charge coupled device) or CMOS device (Complementary Metal Oxide Semiconductor device). Furthermore, as advances in semiconductor manufacturing technology have allowed the pixel size of sensors to be reduced, and the resolution of compact imaging lenses has gradually increased, there is an increasing demand for compact imaging lenses featuring better image quality.
A conventional compact imaging lens assembly for portable electronic products, such as the one disclosed in U.S. Pat. No. 7,145,736, generally comprises three lens elements, in order from an object side to an image side: a first lens element with positive refractive power, a second lens element with negative refractive power, and a third lens element with positive refractive power. However, as advances in semiconductor manufacturing technology will never stop while electronic products are becoming even more compact at the same time, the pixel size of sensors will only become even smaller and the standard for image quality even higher. A conventional lens assembly comprising three lens elements, therefore, is not applicable for higher-end lens modules. U.S. Pat. No. 7,365,920 has disclosed a lens assembly comprising four lens elements, wherein the first and second lens elements are adhered by means of two glass spherical surface lenses to form a doublet so as to correct chromatic aberrations. Such an arrangement of optical elements, however, has the following disadvantages: (1) the degree of freedom in arranging the lens system is curtailed due to the employment of excess number of glass spherical surface lenses; thus, the total track length of the system cannot be reduced easily; (2) the process of adhering glass lenses together is complicated, posing difficulties in manufacture.